Tube-to-tube heat exchanger assembly

ABSTRACT

A tube-to-tube heat exchanger for use in an air conditioning system of a motor vehicle has a unitary tube, which is internally longitudinally divided into a first passage and a second passage by a heat conductive primary web. One warm fluid line is directly connected to each end of the first passage, without the need for a separate connector. One cold fluid return line is directly connected to each end of the second passage, without the need for a separate connector. The fluid lines are connected to the heat exchanger by brazing. In one embodiment, the web is substantially planar and the cross-section of each of the first passage and the second passage is substantially D-shaped. The heat exchanger may further include a support web, extending perpendicularly from approximately mid-way along the primary web. In another embodiment, the cross-sections of the first and second passages may be substantially circular, with the primary web being shaped accordingly. In a further embodiment, the first passage may be substantially circular in cross-section and the second section may be substantially crescent-shaped, with the primary web being shaped accordingly.

FIELD OF THE INVENTION

[0001] The invention relates to heat exchangers and is particularlyconcerned with heat exchangers for use in air conditioning systems ofmotor vehicles.

BACKGROUND OF THE INVENTION

[0002] It is known that an internal heat exchanger (otherwise known as asuction line heat exchanger or simply a heat exchanger) improvesperformance of an air conditioning or refrigeration system by allowingheat transfer between a warm liquid supply line and a cold vapor returnline. The term “internal” in this context means that heat is beingexchanged internally within the system, as compared to a condenser or anevaporator, for example, which exchange heat between the system and theenvironment. One type of internal heat exchanger that could be used inmotor vehicle applications is a “tube-in-tube” or “duplex” heatexchanger where one fluid line extends through the center of the heatexchanger and another fluid line surrounds the first fluid line. Onesuch tube-in-tube heat exchanger is taught in U.S. patent applicationSer. No. 2001/0,020,786 A1, filed on Feb. 23, 2001 in the name ofTakamatsu, et al. However, internal heat exchangers are not typicallyused in motor vehicles, because they tend to be bulky, heavy, and/orexpensive. The tube-in-tube heat exchanger, for example, requires acomplicated connector to separate the fluid line running through thecenter of the heat exchanger from the fluid line that surrounds it. Suchconnectors tend to be relatively large, heavy, expensive, difficult toinstall and they typically cause a significant increase in suction linepressure drop, which results when fluids travel around corners or edges,for example. Such pressure drops reduce the performance of the airconditioning system (or wherever the heat exchanger is located). Inextreme cases, where suction line pressure drop is particularlysignificant, the performance of the air conditioning system may be worsethan if a heat exchanger were omitted from the system.

[0003] In view of the above, it would be desirable to have a heatexchanger that is suitable for use in an air conditioning system of amotor vehicle, that is easily manufactured, that can be easily bent toconform to installation requirements, that has a simple and inexpensiveconnection to the refrigeration or air conditioning system, and thatdoes not add excessive weight, bulk or suction line pressure drop.

SUMMARY OF THE INVENTION

[0004] According to a first aspect, the invention provides atube-to-tube heat exchanger assembly especially for use in an airconditioning system of a motor vehicle, the assembly comprising aunitary heat exchanger comprising a tube internally longitudinallydivided into a first passage and a second passage by a primary web, theprimary web being heat conductive; a first pair of fluid lines; and asecond pair of fluid lines; wherein one line of the first pair of fluidlines is directly connected to one end of the first passage and theother line of the first pair of fluid lines is directly connected to theother end of the first passage and one line of the second pair of fluidlines is directly connected to one end of the second passage and theother line of the second pair of fluid lines is directly connected tothe other end of the second passage.

[0005] The invention could be used in applications beyond the context ofmotor vehicles, in a virtually unlimited range of applications whereheat exchange is necessary or desirable.

[0006] Advantageously, different embodiments of the present inventionmay permit a heat exchanger for use in a motor vehicle that is easy tomanufacture and/or is easy to bend to suit installation requirements,and/or is simply and inexpensively connected to a refrigeration orair-conditioning system and/or does not add significant weight, bulk orsuction line pressure drop.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Preferred embodiments of the invention will now be described withreference to the attached drawings in which

[0008]FIG. 1 is a schematic view of a heat exchanger assembly shownwithin a representative air conditioning system of a motor vehicle;

[0009]FIG. 2a is a perspective view (not to scale) from one end of aheat exchanger, with directly connected fluid lines extending from theheat exchanger, in accordance with an embodiment of the presentinvention;

[0010]FIG. 2b is a perspective view of the heat exchanger and fluidlines of FIG. 2a, from the other end;

[0011]FIG. 2c is a longitudinal sectional view of the heat exchanger ofFIG. 2a;

[0012]FIG. 2d is a cross-sectional view along lines 2 d-2 d of FIG. 2c;

[0013]FIG. 2e is a cross-sectional view along lines 2 e-2 e of FIG. 2c;

[0014]FIG. 3a is a cross-sectional view of a heat exchanger inaccordance with another embodiment of the present invention;

[0015]FIG. 3b is a cross-sectional view of a heat exchanger inaccordance with yet another embodiment of the present invention; and

[0016]FIG. 3c is a cross-sectional view of a heat exchanger inaccordance with yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Referring to FIG. 1, a schematic view of a representative airconditioning system 10 of a large motor vehicle is shown, forillustration purposes. In this example, refrigerant 12 leaves acondenser 14 as a high pressure liquid and flows through an internalheat exchanger (IHX) 18 and then through a thermal expansion valve 20and a rear auxiliary module evaporator 22. The refrigerant 12 leaves therear auxiliary module evaporator 22 as a low pressure vapor and flowsback through the IHX 18 and then through an accumulator 24 and acompressor 26. The refrigerant leaves the compressor 26 as a highpressure vapor and flows through the condenser 14.

[0018] When the refrigerant 12 leaves the condenser 14, it flows alongtwo different paths in this embodiment. One path is through the IHX 18as discussed above. The other path is through an orifice tube 30 andthen through a front module evaporator 32, where the refrigerant 12leaves as a low pressure vapor and then flows through the accumulator24, as described above.

[0019] Referring to FIG. 2a, the IHX 18 is shown in perspective view(not to scale), from one end, with a warm fluid (liquid, in thisexample) supply line 34 and a cold fluid (vapor in this example) returnline 36 extending from the other end the IHX 18. FIG. 2b illustrates theIHX 18 of FIG. 2a in a perspective view from the other end.Cross-sectional views are shown in FIG. 2c (along a longitudinal axis),in FIG. 2d (across the IHX 18), and in FIG. 2e (across the fluid lines34, 36, looking towards the IHX 18). The IHX 18 is a generallycylindrical tube 38, with an internal, heat conductive, generally planarweb 42 which divides the interior area of the IHX 18 into two passages44, 46.

[0020]FIGS. 2a and 2 d illustrate, that in a cross-section across thewidth of the IHX 18, the web 42 creates two substantially D-shapedpassages 44, 46. Ends 48, 50 of the warm liquid supply line 34 and thecold vapor return line 36, respectively, are shaped to fit within thepassages 44, 46, respectively. Although in FIGS. 2a, 2 b and 2 c, thewarm liquid supply line 34 and the cold vapor return line 36 are onlyshown to extend from one end of the IHX 18, in operation, another warmliquid supply line (not shown) and another vapor return line (not shown)would extend from the other end of the IHX 18 in a similar manner, assuggested in FIG. 1. The combination of the IHX 18 directly connected tosupply lines 34 and return lines 36 may be referred to as a heatexchanger assembly.

[0021] The IHX 18 is preferably a single or unitary piece of material,formed by extrusion. Because the purpose of a heat exchanger is totransfer heat, the material should be heat conductive. The IHX 18 ispreferably made from aluminum in view of its cost, weight, heatconductivity, and ability to bend. Other materials that could be usedinclude steel, stainless steel, copper, INCONEL™ material, or plastic.

[0022] The ends 48, 50 of the warm liquid supply line 34 and the coldvapor return line 36 are formed to fit within the passages 44, 46,respectively of the IHX 18 by one of many methods knows to those skilledin the art. One such method involves the use of a machine (not shown)which strikes the end of a fluid line with a punch to create the desiredshape.

[0023] The ends 48, 50 of the warm liquid supply line 34 and the coldvapor return line 36 are then inserted within the passages 44, 46,respectively, and directly connected therein by brazing (not shown). Thetype of brazing material used is dependent, to an extent, upon thematerial used to manufacture the IHX 18, and would be known to thoseskilled in the art. For example, if the IHX 18 is made of aluminum, thenthe brazing material is preferably an aluminum alloy paste, where thepaste is likely a suspension of aluminum in a paste of flux. If the IHX18 is copper, for example, then the brazing material may be silverphosphorous.

[0024] Alternatively, the warm liquid supply line 34 and the cold vaporreturn line 36 could be directly connected to the IHX 18 by staking,where each line 34, 36 would be affixed to the IHX 18 through the use ofmechanical force.

[0025] Prior to affixing the warm liquid supply lines 34 and the coldvapor return lines 36 to the IHX 18, the IHX 18 would be shaped to fit acontour (not shown) where it will be installed in a motor vehicle (notshown). The IHX 18 is shaped using a process known to those skilled inthe art. One such process involves the use of a machine (not shown) toclamp one end or portion of the IHX 18, while another machine (notshown) pushes or pulls another portion of the IHX 18 to bend the IHX 18to create the desired shape.

[0026] As noted above, FIG. 2d is a cross-sectional view of the IHX 18taken along the width of the IHX 18, showing a particular configurationof the web 42. However, the cross-section can be modified by the usedifferent web configurations, for example. One possible modification isshown in FIG. 3a, where the web 42, which may be referred to as aprimary web 42, is essentially the same as that shown in FIG. 2d, with avertical support web 50 added, which provides additional support to theIHX 18 when the IHX 18 is bent. With the embodiment shown in FIG. 2d,the entire primary web 42 can extend, and preferably would extend, thelength of the IHX 18. In the embodiment shown in FIG. 3a, whereas theprimary web 42 can extend the length of the IHX 18, the support web 50terminates at positions (not shown) within the tube 38 approximatelywhere the end of the supply lines 34 or the return lines 36 would beaffixed to the IHX 18, since otherwise, the support web 50 would preventthe supply lines 34 or the return lines 36 from being pushed within theIHX 18. The supply lines 34 and the return lines 36 would then beaffixed to the IHX 18 as described above.

[0027] Another variation of a web configuration is shown in FIG. 3b. Inthis embodiment, one pair of fluid lines, likely (although notnecessarily) the return lines 36, would have their ends shaped in acircular form (not shown) to fit within the substantially circular area54 created by the primary web 56 (unless the ends of the return lines36, in their original form, would fit within the area 54 without theneed for modification). Similar to the embodiment described above withrespect to FIG. 3a, the support web 58 of FIG. 3b does not extend thelength of the tube 38. Rather, the support web 58 terminates atpositions (not shown) within the tube 38 approximately where the ends ofthe supply lines 34 (or the return lines 36, as the case may be) wouldbe affixed to the IHX 18. In this embodiment, an end portion of eachsupply line 34 would then be shaped as a crescent to fit within the tube38. The supply lines 34 and the return lines 36 would be affixed withinthe IHX 18 as described above.

[0028] Another embodiment is shown in FIG. 3c, where both the shape ofthe tube 38 and the web configuration are different from those describedabove. In the embodiment shown in FIG. 3c, the cross-sectional view ofthe tube 38 is substantially peanut shaped, with a primary web 62defining two circle-shaped passages 64, 66. In this embodiment, the endportions of the supply line 34 and return line 36 may be able to fitwithin the passages 64, 66, respectively, of the IHX 18 withoutmodification. However, the circular profiles of the passages 64, 66 mayprovide limited heat exchange, due to the reduced surface area, ascompared to the web configurations in the other embodiments. As well,the circular profiles of the passages 64, 66 may restrict bending of theIHX 18, other than in the horizontal plane.

[0029] Numerous modifications and variations of the present inventionare possible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practised otherwise than as specifically described herein. Forexample, while the IHX 18 above has been described as being primarilyfor use in an air conditioning application of a motor vehicle that has arear auxiliary module and conventional refrigerant, the IHX 18 could beused for other applications within a motor vehicle. For example, the IHX18 could be used in a vehicle with a front module only, or with otherrefrigerants such as carbon dioxide or ammonia. In another example, theIHX 18 could be used as part of a heat pump or short-cycle system towarm up or extract heat from the engine coolant, to produce heat for apassenger compartment of the motor vehicle. It could also be used tocool engine, transmission or transaxel fluids. Moreover, the IHX 18could be used in applications beyond the context of motor vehicles,where heat exchange is necessary or desirable. For example, the IHX 18could be used in the chemical process industry or anywhere aninexpensive heat exchanger is needed. As another example, the IHX 18could be used in domestic water heaters for pools or spas based onrefrigerant cycles, for instance, or in hot water space heating systems.

1. A tube-to-tube heat exchanger assembly especially for use in an airconditioning system of a motor vehicle, the assembly comprising aunitary heat exchanger comprising a tube internally longitudinallydivided into a first passage and a second passage by a primary web, theprimary web being heat conductive; a first pair of fluid lines; and asecond pair of fluid lines; wherein one line of the first pair of fluidlines is directly connected to one end of the first passage and theother line of the first pair of fluid lines is directly connected to theother end of the first passage and one line of the second pair of fluidlines is directly connected to one end of the second passage and theother line of the second pair of fluid lines is directly connected tothe other end of the second passage.
 2. The assembly of claim 1, whereinthe first pair of fluid lines are warm fluid supply lines and the secondpair of fluid lines are cold fluid return lines.
 3. The assembly ofclaim 1, wherein the primary web is substantially planar.
 4. Theassembly of claim 1, wherein the heat exchanger is an extrusion.
 5. Theassembly of claim 1, wherein the heat exchanger is made of aluminum. 6.The assembly of claim 1, wherein each of the first passage and thesecond passage, in end view, is substantially “D” shaped.
 7. Theassembly of claim 6, wherein an end of each of the warm fluid supplylines and the cold fluid return lines is substantially “D” shaped in endview.
 8. The assembly of claim 1, wherein each of the first passage andthe second passage, in end view, is substantially circular.
 9. Theassembly of claim 1, wherein each of the warm fluid supply lines and thecold fluid return lines is directly connected to the heat exchanger bybrazing.
 10. The assembly of claim 7, wherein the heat exchanger furthercomprises a longitudinal support web extending from the primary web tothe tube.
 11. The assembly of claim 10, wherein, in an end view, theprimary web and the support web together appear substantially T-shaped.12. The assembly of claim 11, wherein the primary web extendslongitudinally substantially the entire length of the tube.
 13. Theassembly of claim 12, wherein the support web terminates a distance fromeach end of the tube to allow for insertion of the warm liquid supplylines or the cold vapor supply lines into the tube.
 14. The assembly ofclaim 1, wherein the primary web, in end view, is substantiallyarc-shaped, with ends of the primary web terminating at positions on aninner circumference of the tube, thereby creating the first passagehaving a substantially crescent-shape and the second passage having asubstantially circular shape.
 15. The assembly of claim 14, wherein theheat exchanger further comprises a support web, being substantiallyplanar, and in an end view, the support web extending from approximatelymid-way along the primary web, away from the primary web, to the innercircumference of the tube.
 16. The assembly of claim 15, wherein eachline of the first pair of fluid lines, in an end view, is shaped toconform to the cross-section of the second passage, and each line of thesecond pair of fluid lines, in an end view, is shaped to conform to thecross-section of the first passage.
 17. The assembly of claim 16,wherein the primary web extends substantially the entire length of thetube.
 18. The assembly of claim 17, wherein the support web terminates adistance from each end of the heat exchanger to allow for insertion ofthe warm liquid supply lines or the cold vapor supply lines into thetube.